From 1889 to 1895 the Manchester Ship Canal Company constructed a canal to enable ocean-going vessels of up to 18,000 tons displacement to sail up to Manchester from the Mersey estuary via Runcorn and Warrington, bypassing the port of Liverpool. Ships pass through five sets of locks on their way between Eastham and Manchester, which lift them a total of 19 metres above the mean tide level of the estuary. The Ship Canal incorporated reaches of a number of rivers, notably the Irwell and the Mersey and all the flows from the catchment areas of the Irwell, Upper Mersey and the Weaver enter the Canal. Prior to the construction of the Canal, the Irwell had a history of flooding between Manchester and Runcorn. During a visit to Manchester in 1729, Daniel Defoe reported that the town had a bridge "built so high because floods could cause the river to rise four or five yards in a night".
The Ship Canal must be dredged continually of the sediment that is brought into it and accumulates on the bed of the Canal, and also in the Approach Channel to Eastham Locks, in order to maintain sufficient draught for navigation. Dredged sediment is disposed of by pumping it into specially-constructed deposit grounds adjacent to the Canal. The principal deposit grounds are situated at Frodsham on the Mersey estuary and at Woolston, east of Warrington.
The Manchester Ship Canal Company also has to maintain a large number of locks and sluices, and conduct routine maintenance and remedial repairs of the Canal slopes and banks, fixed bridges and swing bridges. For example, the sluices at the mouth of the river Weaver allow flood waters to be diverted into the Mersey estuary, while upstream, sluices at Latchford protect Warrington from flooding.
In 1887 the Ship Canal Company purchased the Bridgewater Canal, which had been constructed in the 1760s between Manchester and the Mersey estuary at Runcorn, with a branch to Leigh and the Duke of Bridgewater's collieries at Worsley. The Leigh branch was severely affected by mining subsidence, requiring the canal banks to be raised repeatedly. In addition, the Ship Canal Company owned and operated an extensive network of railways.
In March 1974 Peter Rowe stated that he had advised the Manchester Ship Canal Company for 21 years on a great variety of problems and proposals, such as those concerning docks, training walls for locks, canal slope protection, sludge deposit grounds, and wharf structures, and that no year had passed without a number of jobs being in progress. In fact Rowe worked for the company well into his retirement; the most recent archive material dates from 1994.
The Manchester Ship Canal Company material includes papers relating to dredging tests at Arpley on the river Mersey; works and tests at Latchford locks and jetties; reports and tests on deposit grounds, especially those at Frodsham and Woolston; reports on various canal bank repairs and remedial works to counter erosion and to improve slope stability; bridge reconstruction projects; reports and tests on the construction of warehouses, transit sheds and jetties; and papers relating to mining subsidence on the Bridgewater Canal and an embankment collapse near Dunham Massey. PWR/4/1/23 contains information on the history of the Ship Canal.